Mold and method of manufacturing the same

ABSTRACT

A mold welded with a dissimilar metal member, characterized in that said mold is manufactured by a method comprising a first step for pressingly bringing the dissimilar metal member into contact with a mold formed of copper or a copper alloy in a stationary state while rotating the dissimilar metal member at a high speed, a second step for stopping the dissimilar metal member, and a third step for providing a forced pressure larger than the pressure in the first step to the mold. By utilizing the present mold, the problems of efficient cooling and attachment of back frame are solved, more concretely, a variety of problems such as cutting processing loss of copper or a copper alloy plate, a large amount of processing time, heat distortion and heat deterioration of a copper plate and the like can be solved, and the reliability concerning with the welding position precision and the welding strength of stud bolt can be improved. A mold welded with a dissimilar metal member characterized in that the mold is manufactured by a method comprising a first step.

FIELD OF THE INVENTION

The present invention relates to a mold which is welded with adissimilar metal member and is formed of a copper or a copper alloy as abase metal, and a method of manufacturing the same.

BACKGROUND ART

Conventionally, in the field of iron and steel industry, molten steelreaching to about 1500° C., which has been taken out from a steel makingfurnace such as a converter, an electric furnace or the like, isserially sent to a casting mold made of copper or a copper alloy havinga cooling mechanism on the back face (rear face) via ladle, tundish andtundish nozzle, while reducing the temperature by bringing the moltensteel into contact with the mold wall, is discarded in a lower directionwhile it gradually forms a thick solidification shell and is allowed tomake a slab which is serially formed and has a certain size.Furthermore, subsequently, it is sent to the tail end processes such asheating, rolling and the like and then, it is made into a product viacutting off process. Copper or a copper alloy having a high thermalconductivity is usually utilized for such continuous casting moldmaterial for steel, since it has an important function for reducing thetemperature from the molten steel.

As described above, although it is needless to say with respect to thecontact surface with the molten steel of a mold that the considerationson an effect of reducing the temperature by utilizing copper or a copperalloy having a high thermal conductivity as a material and so on havebeen done. However, the surface hardening accompanying with the growthof solidification of the molten steel has been progressed, and since thecopper member is weared by such surface hardening and the like, asurface cracking which is called as a star crack is occurred by mixingcopper into the slab, the prevention of the damage to the slab occurringby utilizing copper as well as the countermeasures of the wear have beenconventionally carried out by coating nickel, nickel-cobalt alloy,nickel-iron alloy, nickel-chromium alloy or the like on the contactsurface with the molten steel in the mold, using a method of plating, amethod of thermal spraying or the like.

With respect to a cooling mechanism installed at the back face of acontinuous casting mold, it has a structure in which a back frame (waterbox) has been attached on the anti-molten steel contact surface of thecasting mold as shown in FIG. 7. For example, as shown in FIG. 3, it hada structure in which a hole for a back frame mounting member and acooling groove for enhancing the cooling efficiency have been alsoprovided on the mold itself. It is natural that the shape and the numberof such grooves are accompanied by some changes depending on theconditions specific to the continuous casting machine, however, thethickness of the copper member or copper alloy member used for thiscasting mold is almost fixed basically in the range from 40 to 50 mm. Itshould be noted that in apart of the casting field, a continuous castingmachine having a so-called electromagnetic stirring function, i.e. thestirring function of the molten steel within the mold by electromagneticforce, has been employed for the purpose of contemplating theimprovement of central segregation of the slab and the solidificationstructure and making the slab with a higher quality, and in recentyears, its use has been increased.

The casting mold which is used in a continuous casting machine with anelectromagnetic stirring function is often set in a thinner mold thanthe usual mold, and the thickness of copper member or a copper alloymember is often set in the range from about 25 to about 30 mm for thepurpose of enhancing permeability and because the temperature of thecasting upper portion is tended to rise by the effect of the moltensteel stirring within the mold. Therefore, a certain device is also madeto the back frame, however, the thinning of the copper member or thecopper alloy member makes it difficult to provide a hole into which theback frame is to be mounted.

Furthermore, in an example of a casting mold which is used in somecontinuous casting machines with an electromagnetic stirring function,such mold employs a structure in which the back frame is mounted bywelding pieces of stud bolts made of stainless steel in a pitch rangefrom 150 to 200 mm by an arc stud welding method as it is in a state offlat surface without providing a cooling groove on the back face fromthe first. The arc stud welding method is a method wherein a base metaland a portion of stainless steel are melted and welded by generating anarc under the direct current electric source. However, since the objectmatter (base metal) is copper or an alloy made with copper which has ahigh thermal conductivity, and since the object matter (base metal) hasa heat discharging volume much larger than the stud bolt (made ofstainless steel) which is to be welded, it must be said that highlyexcessive heat input is applied from the viewpoint of the weldingconditions. As a result of this, it is difficult to avoid that thematerial is subjected to the influence of the heat over the wide zone.In addition to this, in this process, it requires a ring made of ceramicin a cylinder shape which is called ferrule and having the all offunctions of edge preparation of stud bolt edge, combination use offlux, dispersion prevention of the melted metal, and electricinsulation, and thus the welding operation becomes complex andtroublesome. Moreover, the casting mold in which the required number ofstud bolts have been welded accompanies the variation of 1.6 mm or thelike from the viewpoint of a perpendicular degree to the mold coppermember, and in addition to the problem of preciseness of mounting studbolt, it often shows such defects that the heat deformation and strengthdeterioration of the copper plate, the cracking of the copper member ata higher or lower temperature of the welding portion between the copperplate and stud bolt occur, and the melted slag remains without beingcompletely exhausted from the welded portion between the copper plateand stud bolt. These complex factors require, in some cases, re-weldingworking, and cause bolt broken incident at the time of back frameassembling, and further, bolt breakage incident by various kinds ofaction stresses during the mold operation and the like. In FIG. 2(a) andFIG. 2(b), the states of before the arc stud welding is performed andafter the arc stud welding has been performed is shown in a summarydiagram.

Furthermore, as an embodiment of mold which is utilized in a continuouscasting machine accompanied with another electromagnetic stirringfunction as shown in FIG. 4, there is also exemplified such an examplehaving a structure wherein only the copper member of the back frameattachment portion is thicker, a back frame attachment seat is providedby performing the screw hole processing to the structure which has beenmade thicker and further, a cooling groove is provided by performing thecutting processing. In such an example, there is no heat inputaccompanied with an arc stud welding, and there is also no fear aboutthe raw material deformation and strength deterioration since the backframe mounting seat in a cylindrical shape is provided on the rearsurface of the copper member, and cooling grooves at other sites exceptfor the rear surface are processed. On the other hand, it cannot helpbecoming a complex processing of the processing of mounting seat, theprocessing of back frame mounting hole (screw hole processing and tappfor HELI-COIL insert (hereinafter, referred to as helisert) made ofstainless steel mounting) and the like. Further, 40 to 50% by weight ofthe original copper or copper alloy member is actually cut and removedby this serial mechanical processing. The cut pieces will be utilized inany way as refreshable scraps, however, it accompanies the occurrence ofa large amount of industrial waste.

As described above, in the case of a conventional casting mold, for thepurpose of setting the back frame mounting hole and imparting thefunction of efficient cooling, the processing such as the processing ofmounting hole, the fitting of a helisert made of stainless steel for thepurpose of enhancing and protecting a screw thread, and further theprocessing of a cooling groove which is to be a pathway of cooling waterand the like is performed on the back face of the thick copper member.On the other hand, in a casting mold in the casting machine having theconventional electromagnetic stirring function, there is used an arcstud welding method in which there are many problems in view of heatdeformation of the material, strength deterioration, welding defects,welding position preciseness and the welding strength, or there isperformed the processing of back frame mounting seat, the attachment oftapp for HELI-COIL insert (hereinafter, referred to as helisert) made ofstainless steel, the processing groove or the like which is accompaniedwith a long time processing and the material loss from the thick coppermember. In this way, it is understood that the technical problems commonto the conventional anti-molten steel contact surface (rear surface) ofsteel continuous casting mold are largely summarized to two problems ofefficient cooling and .the mounting of back frame. More concretely,solution of the various problems such as improvements in cuttingprocessing loss of copper member or a copper alloy member, long time ofprocessing, precision of welding position with respect to copper memberor a copper alloy member, reliability of welding strength, and heatdeformation and heat deterioration of copper member and the like,contributes to the saving of the resources, the reduction of industrialwaste, the shortening of the processing time, and the enhancement of thereliability in the welding between the copper alloy member and studbolt, therefore, which contribution is enormous to the industries.

Moreover, a large problem of the casting mold in which the conventionalgeneral cooling groove is provided by performing the cutting processingis in that from the necessity of providing a mounting hole for thepurpose of mounting the back frame on the side of the copper plate, thecopper plate is confined to a thicker one and the use of the thickercopper plate causes the processing of a cooling groove. If a novelmethod of mounting a back frame which solves such a problem is found,the thinning of the copper plate and the processing of a cooling groovethemselves can be made null, the problem of the copper plate used forthe electromagnetic stirring of a method in which the thicker copperplate is still used for the purpose of providing a back frame mountingseat is also solved.

Moreover, in the case of the mold copper plate for electromagneticstirring which utilizes an arc stud welding method of stud bolt, if astud bolt welding method which can improve the welding positionprecision and the welding strength as well as the heat deformation andheat distortion of the copper plate can be suppressed is found, theposition leveling of bolt, stud bolt breakage incident and the like canbe avoided.

SUMMARY OF THE INVENTION

Therefore, the present invention is to provide a mold for solving theproblems of efficient cooling and mounting of back frame, and moreconcretely, to provide a mold for solving the problems such asimprovements in cutting processing loss of a copper member or a copperalloy member, a large amount of the processing time period, reliabilityof the welding position precision and the welding strength of studbolts, heat deformation and heat deterioration of the copper member andthe like.

In order to solve the above problems, the present inventors haveinvestigated various studies by means of try and error. As a result ofthese studies, the present inventors have succeeded in producing a moldwelded with a dissimilar metal member, characterized in that the mold ismanufactured by a method comprising a first step for pressingly bringingthe dissimilar metal member into contact with a mold formed of copper ora copper alloy in a stationary state while rotating the dissimilar metalmember at a high speed, a second step for stopping the dissimilar metalmember, and a third step for providing a forced pressure larger than thepressure in the first step to the mold. Thus, the present inventors havefound that the present invention can solve the various problems such ascutting process loss of a copper member or a cooper alloy member, alarge amount of processing time period, reliability of the weldingposition precision and the welding strength of stud bolt, heatdeformation, heat deterioration of the copper member and the like, thatis, the above-described problems are solved at once.

After the present inventors have acquired such various findings, theyfurther studied intensively and completed the present invention.

Specifically, the present invention relates to:

(1) a mold welded with a dissimilar metal member characterized in thatthe mold is manufactured by a method comprising a first step forpressingly bringing the dissimilar metal member into contact with a moldformed of copper or a copper alloy in a stationary state while rotatingthe dissimilar metal member at a high speed, a second step for stoppingthe dissimilar metal member, and a third step for providing a forcedpressure larger than the pressure in the first step to the mold,

(2) the mold according to the above (1), characterized in that the moldis a steel continuous casting mold,

(3) the mold according to the above (1) or (2), characterized in thatthe dissimilar metal member is a back frame mounting member,

(4) the mold according to the above (3), characterized in that the backframe mounting member is equipped with a screw structure for interiorlymounting the back frame,

(5) the mold according to the above (2), characterized in that the steelcontinuous casting mold is a steel continuous casting mold forelectromagnetic stirring,

(6) the mold according to the above (1), characterized in that mainrotation speed of the dissimilar metal member of the first step is 60m/min or more, the pressure is 40 MPa or more, and the forced pressureof the third step is 60 MPa or more,

(7) the mold according to the above (1), characterized in that thedissimilar metal member comprises a stainless steel, titanium, atitanium alloy or a nickel alloy,

(8) the mold according to the above (1), characterized in that when amold and a dissimilar metal member are brought into contact with eachother, a nickel plating layer or a nickel alloy plating layer, or anickel foil or a nickel alloy foil is intervened between the moldsurface and the dissimilar metal member surface.

(9) the mold according to the above (8), characterized in that thethickness of a plating layer or a foil is in the range from 1 to 50 μm,

(10) a method of manufacturing a mold welded with a dissimilar metalmember characterized in that the method comprises a first step forpressingly bringing the dissimilar metal member into contact with a moldformed of copper or a copper alloy in a stationary state while rotatingthe dissimilar metal member at a high speed, a second step for stoppingthe dissimilar metal member, and a third step for providing a forcedpressure larger than the pressure in the first step to the mold,

(11) a method of manufacturing a mold welded with a dissimilar metalmember, characterized in that while performing pressure welding of themold and the dissimilar metal member, said mold and mold metal memberare subjected to solid state welding by friction heat generated by thedifference of both main spindle rotation speeds,

(12) the method of manufacturing according to the above (11),characterized in that the surface area of welding surface includingwelding site of a mold which consists of copper or a copper alloy is100-fold or more of the welded area of a dissimilar metal member,

(13) a steel continuous casting mold in which a back frame mountingmember welded by friction welding, and

(14) the method of manufacturing according to the above (1),characterized in that the forced pressure of the third process is 2 to3-fold of the pressure of the first process.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a sequence of friction welding in the present invention.

FIG. 2 is a drawing illustrating a conventional arc stud welding method,wherein (a) shows the state before the arc stud welding, and (b) showsthe state after the arc stud welding.

FIG. 3 is a cross sectional plan view of a conventional general castingmold.

FIG. 4 shows an embodiment of a conventional casting mold forelectromagnetic stirring.

FIG. 5 is a schematic view showing a mold of the present invention.

FIG. 6 shows hardness measurement sites of test pieces in Example 2.

FIG. 7 is a perspective view showing the casting mold mounted on theback frame.

In the Figures, the numeral 1 denotes stud bolt, the numeral 2 denotesferrule, the numeral 3 denotes copper or a copper alloy, the numeral 4denotes flux, the numeral 5 denotes excess metal portion, the numeral 6denotes heat-affected zone, the numeral 7 denotes molten steel contactsurface, the numeral 8 denotes cooling groove, the numeral 9 denotesback frame mounting hole, the numeral 10 denotes back frame mountingseat in a cylindrical shape, the numeral 11 a denotes boss made ofstainless steel, the numeral 11 b denotes boss made of stainless steel,the numeral 12 denotes back frame and the numeral 13 denotes castingmold.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention relates to a mold welded with a dissimilar metalmember, characterized in that the mold is manufactured by a methodcomprising a first step for pressingly bringing the dissimilar metalmember into contact with a mold formed of copper or a copper alloy in astationary state while rotating the dissimilar metal member at a highspeed, a second step for stopping the dissimilar metal member, and athird step for providing a forced pressure larger than the pressure inthe first step to the mold.

The present inventors have compared and investigated a variety ofcasting molds. As a result of the investigation, the present inventorshave noticed that if different materials, for example, such as stainlesssteel material or the like are able to be welded with a great strengthwithout heat deterioration of the material to copper and its alloymaterial which is excellent in thermal conductivity, instead of workingin providing hole for back frame which is common to many casting mold,various general problems over the casting mold can be solved at once,and a novel casting mold can be provided. Then, the present inventorshave compared and studied in detail methods of welding various materialsincluding welding again. First, as a method of welding that the presentinventors have investigated, there are exemplified arc welding withcovered electrode, gas shield arc welding with consumable electrode,self-shield arc welding, submerged arc welding, electroslag welding,electrogas arc welding, stud welding, electron beam welding, laserwelding, magnetic drive arc welding, oxygen-acetylene welding, and thelike, and the present inventors have studied a variety of such weldingmethods. However, most of the welding methods are welding methods thatare largely affected by heat, or are applied in a special requiredatmosphere, and thus these methods could not essentially solve theproblem.

Then, the present inventors have paid attention to the potentiality offriction welding as a solid state welding method that were capable ofautomating and mechanizing the welding from about the middle of 1960s,the heat-affected zone is extremely limited and it is expected that onlythe welded surface are exothermic, and investigated the potentiality ofapplication of welding method to copper plate, stainless steel memberand titanium member. When welding combinations through friction weldingare taken into consideration, in any case, aluminum and its alloy,copper and its alloy, carbon steel, alloy steel, stainless steel and thelike are classified in the welding possible zone with respect to copperor a copper alloy. However, as a practical problem, there has been noexample that a material having an excellent thermal conductivity and alarge volume, and a dissimilar material having an extremely small volumeare practically used, and casting mold is just the case. Specifically,in the casting mold, there is too much difference of size for theviewpoint of volume between the metal member to be welded and thedissimilar metal member, and the mold member itself becomes an excellentefficient heat discharging plate. Therefore, even if the welding itselfbetween metal member and dissimilar metal member could be carried out,it was feared that the contents of the welding from the viewpoint ofwelding strength and the like could not be satisfied. Practically, apreliminary test was performed wherein stainless rod as a weldingmember, and copper rod having approximately the same size as a member tobe welded are welded, revealing that the welding itself was possible.Then, when the copper rod was changed into a copper plate having a sizeof 150 mm square×25 mm thickness, and the stainless rod was changed intoa stainless rod having a diameter of 14 mm, the welding test wascontinued. As the present inventors have feared, a zone having voids andnot having been welded in the welding interface zone over wide range hasbeen generated. Moreover, the formation of the mixed layer of thestainless steel and copper in the vicinity of the interface was notenough, too, and an excellent welding strength could not be expected.However, since the welding was attained even though it was partial, itis expected that there is a possibility of welding, and then a weldingtest at full scale using the combination between chromium/zirconiumcopper member and SUS304 member was started. As a result of this test,the present inventors have found that in order to obtain the stable andstrong welding, three conditions including friction pressure, rotationspeed of the main spindle, and forced pressure (hereinafter, referred toas upset pressure) are dominant in the welding. Further, the presentinventors have found that when the welding is performed via a first stepof contact under a pressure while rotation at a high speed, a secondstep of stopping the high speed rotation, and a third step of applying aforced pressure larger than the pressure in the first process, thewelding is excellent and satisfactory. Further, the present inventorshave found that in the case where the conditions in each step are suchthat friction pressure is about 40 MPa or more, upset pressure is about60 MPa or more, and main spindle rotation speed is about 60 m/min ormore, a preferred welding showing a welding strength stronger than thetensile strength of the copper plate. It should be noted that thepresent inventors have found that it is preferred that the main spindlerotation speed is about 2000 rpm or more.

Furthermore, the present inventors have found that if the setting iswithin the above-described conditions, the setting of conditionsexceeding over or largely exceeding over the friction pressure of about40 MPa, upset pressure of about 60 MPa and the main spindle rotationspeed of about 60 m/min can provide quality level without any problemfrom the viewpoint of welding strength and interface structure.Specifically, the present inventors have found that the more the numberof the above-described three conditions is made larger (made conditionssevere), the more burr generation volume accompanied with frictionwelding is tend to be increased. However, since such level of weldingstrength is saturated, there is not any meaning except that an excellentwelding and the like are obtained as described above even if theexcessive severe conditions are set. Furthermore, the present inventorshave found that by performing an experiment using a stainless steel, andfurther by performing an experiment using a titanium member as adissimilar metal member instead of stainless steel member, a variety oftendencies seen in the stainless steel member concerning with thewelding are also approximately the same with titanium member and thelike.

Moreover, the present inventors have made various investigations for thepurpose of enhancing interface heat input amount at the welding, makingthe welding more stable, and improving the welding strength. As aresult, in the case where a copper plate and a rod made of stainlesssteel are welded by the above-described friction pressure method bycovering nickel, nickel alloy or the like which is inferior to copper inview of thermal conductivity, on the side of the copper plate or in thevicinity of the point of the stainless steel, or by interposing a foilsuch as the nickel member or nickel alloy plate, the rise of frictiontorque can be seen, the interface heat input efficiency at the time ofwelding can be enhanced, and the welding can be made more stable, whichis useful for achieving the above-described object and the like.Furthermore, the present inventors have found that in order to obtainmore preferable results, it is preferred that the thickness of coatingor foil is in the appropriate range, it is preferred that the thicknessof coating or foil is in the range from about 1 to 50 μm and it is morepreferable that it is in the range from about 2 to 20 μm.

Moreover, the present inventors have found that from the viewpoint thatchange in color caused by heat on the periphery of the welding portioncan be avoided, the plating on the side of copper plate is morepreferred than the plating (covering nickel or nickel alloy) on the sideof stainless steel (in the vicinity of the tip part of rod made ofstainless steel). However, it has been found that the effect from theviewpoint of strength obtained by interposing nickel or its alloyintermediately was not seen so much compared to the case where these arenot interposed, and intensiveness of the variation of the weldingstrength was seen. The present inventors have found that for example,the welding strength at the time when the welding strength at the copperplate and rod made of stainless steel were welded without interpositionof the foil such as nickel, its alloy or the like are varied from 50 to60 MPa even if these are welding conditions described above, and to thecontrary, at the time when the copper plate and rod made of stainlesssteel are interposed, it is possible that the variation range is madenarrower to 20 to 30 MPa and the like. Thereafter, based on thesefindings, the present inventors have found that the variation of thewelding strength can be made narrower by interposing the foil such asnickel, its alloy or the like at the time of the above-describedwelding.

A preferred embodiment of the present invention will be described belowwith reference to FIG. 1.

The welding of the mold and a dissimilar metal member is achieved by (a)fixing the mold and gradually raising the main spindle rotation speed ofthe dissimilar metal member, (b) maintaining the main spindle rotationspeed of dissimilar metal compound at the time when the main spindlerotation speed has reached to the desired value, (c) bringing thedissimilar metal compound into contact with the mold under the pressurefor a desired time period, thereby to generate the friction heat, (d)reducing the main spindle rotation speed of the dissimilar metal memberusing a brake while maintaining the pressure, and (e) applying thedesired above-described upset pressure.

In short, the gist of the present invention resides in that the mold andthe dissimilar metal member are subjected to solid state welding, usingthe friction heat generated by the difference of both main spindlerotation speeds in the state where the mold and the dissimilar metalmember are welded.

Although the copper alloy which is used in the present invention is notparticularly limited, a conventional alloy in this technical field isappropriately used. For example, there are exemplified a copper platefor a mold, obtained through precipitation hardening by the addition ofchromium/zirconium (for example, Cr: 0.5-1.5% by mass, Zr: 0.08-0.30% bymass, and the remaining portion: Cu), and a chromium/zirconium/aluminumaddition copper plate for a mold with electromagnetic stirring (forexample, Cr: 0.50-1.50% by mass, Zr: 0.08-0.30% by mass, Al: 0.7-1.1% bymass, and the remaining portion: Cu) and the like.

Referring to the dissimilar metal member which is used in the presentinvention, any species is available if it is a metal except for copperor a copper alloy, and it may include aluminum or its alloy, carbonsteel, alloy steel, and stainless steel, and the like, however,preferable examples of such dissimilar metal members are stainlesssteel, titanium, a titanium alloy or a nickel alloy. Moreover, accordingto the present invention, it is preferable that the above-describeddissimilar metal member is a back frame mounting member, and that theback frame mounting member is one in which a screw structure formounting the back frame has been interiorly provided.

The preferable kinds and conditions of nickel plating solution (bath)are listed below.

As a plating solution for obtaining nickel, there are many platingsolution, for example, a Watt's bath, a borofluoride bath, a sulfatebath with high concentration, a sulfamate bath, a nickel ammoniumchloride bath, a nickel ammonium sulfate bath and the like, and all ofthese can be utilized, however, most of the baths are bad in workingefficiency and strong in toxicity, and most preferable bath is a Watt'sbath and a sulfamate bath.

(1) Watt's bath pH 3-5 nickel sulfate (6H₂O) 230-360 g/L nickel chloride(6H₂O) 20-60 g/L boric acid 25-45 g/L anti-pitter used in combination ifrequired brightener not used current density 1-6 A/dm² temperature40-70° C. agitation air agitation

(2) sulfamate bath pH 3-5 nickel sulfamate (4H₂O) 300-600 g/L nickelchloride (6H₂O) 0-30 g/L boric acid 25-45 g/L anti-pitter 0.3-1.0 g/Lcurrent density 1-10 A/dm² temperature 30-60° C. agitation with orwithout pump agitation

The kinds and appropriate conditions of nickel alloy plating solutionwill be described below.

As a nickel alloy plating, there can also be used a nickel-iron alloy,and a nickel-cobalt alloy.

(1) Example of nickel-iron alloy a. sulfamate bath pH 1-3.5 nickelsulfamate (4H₂O) 300-600 g/L nickel chloride (6H₂O) 0-15 g/L ferroussulfamate 0.5-10 g/L sodium citrate 10-30 g/L boric acid 25-45 g/Lsodium lauryl sulfate 0.3-1.0 g/L current density 1-6 A/dm² temperature40-60° C. agitation with or without pump agitation b. sulfate bath pH1-4 nickel sulfate (6H₂O) 80-250 g/L nickel chloride (6H₂O) 40-60 g/Lferrous sulfate (7H₂O) 1-40 g/L sodium citrate 2-20 g/L sodium gluconate2-20 g/L additive 0.1-1 g/L current density 1-10 A/dm² temperature45-65° C.

(2) Example of nickel-cobalt alloy a. sulfamate bath pH 3-5 nickelsulfate (6H₂O) 100-200 g/L cobalt sulfate (7H₂O) 50-150 g/L nickelchloride (6H₂O) 15-40 g/L boric acid 25-45 g/L sodium lauryl sulfate0.3-1.0 g/L current density 1-10 A/dm² temperature 45-60° C. agitationwith or without agitation using a jet pump b. sulfate bath pH 3-5 nickelsulfate (6H₂O) 100-200 g/L cobalt sulfate (7H₂O) 50-150 g/L nickelchloride (6H₂O) 15-40 g/L boric acid 25-45 g/L anti-pitter 0-20 mL/Lelectric current density 1-10 A/dm² temperature 40-60° C. agitation withor without pump agitation

Examples of the steps for plating copper or copper alloy with nickel ora nickel alloy are described below.

(1) In order to plate nickel or nickel alloy on the side of a copperplate, the surface to be covered or the portion except for covering ismasked by a paint having a chemical resistance or a tape, and afterimmersion degreasing, water washing, acid immersion, washing usingwater, and nickel plating or nickel alloy plating may be performed bythe normal method. That is, after a commercially available degreasingagent 100 HK (manufactured by Uken Industries Co., Ltd.) as an immersiondegreasing solution is applied for 5 minutes at 60° C., followed bywater rinsing, activation was performed by immersion in 98% sulfuricacid of 50 mL/L for 3 minutes at room temperature, water rinsing wasagain made, and then nickel plating is carried out. It should be notedthat any one of plating solutions can be utilized, however, for example,nickel plating is carried out under the following conditions usingWatt's bath: pH 4.2 nickel sulfate (6H₂O) 240 g/L nickel chloride (6H₂O)45 g/L boric acid 30 g/L current density 3 A/dm² temperature 50° C.agitation air agitation

(2) On the other hand, when nickel plating is carried out on the side ofstainless steel bolt or rod, the following step is employed.Specifically, after the rod is masked while leaving or not leaving thearea in the vicinity of the welding surface of the stainless steel rod,immersion degreasing is first performed in the same manner as in coppermember, and the rod is rinsed using water, and subsequently immersed in37% hydrochloric acid solution of 500 mL/L for 5 minutes, followed byrinsing with water. Next, after a strike plating is carried out in astrike plating solution comprising nickel chloride (6 H₂O) of 200 g/L,37% hydrochloric acid of 70 mL/L for 3 minutes at room temperature andat a current density of 5 A/dm², the rod is rinsed using water, andnickel plating is carried out under the same conditions with the coppermember.

In the present specification, the symbol of “%” denotes “% by weight”unless otherwise specified.

Hereinafter, the detail of the contents of the welding test will bedescribed with reference to Examples/Comparative Examples.

EXAMPLES Example 1 and Comparative Example

As a chromium/zirconium copper, 150 mm square×25 mm thickness memberselected from CCM-B made by Chuetsu Alloy Molder Industries Co., Ltd.(chemical component: Cu: >98.0% or more, Cr: 0.5-1.5%, Zr; 0.08-0.30%)was prepared, and it was set on the fixed side. For movable side, a rodmember made of SUS304 corresponding to stud bolt was selected, and a rodhaving the size of 14 mm diameter×70 mm length was used. It should benoted that the pressure welding was repeated in the range of parameterconditions shown in Table 1. The representative sequence at the time offriction welding is shown in FIG. 1. The abstract from the test resultsis indicated in Table 2. From these results, the most preferable rangefor pressure welding conditions showed that the main spindle rotationspeed is 130 m/min. or more, the friction pressure (P₁) is 60 MPa ormore, the friction time (t₁) is in the range from 2 to 20 seconds, theupset pressure (P₂) after the main spindle rotation speed was made 0m/min. by making the brake work is 150 MPa or more, and the upsetmaintaining time (t₂) is in the range of about 5 to 30 seconds. Also inthe tensile test (universal tensile testing machine made by Shimadzu)and cross sectional micro-observation (optical microscope made byOlympus), the welding strength (tensile strength) of chromium/zirconiumcopper and stainless steel (SUS304) shows 400 N/mm² or more within theabove-described appropriate conditions range, and also in theobservation of the cross sectional micro-structure, the defects were notfound, and it could be enough to be applied into practical use. For anexcellent welding, it has been found that three factors of frictionpressure, main spindle rotation speed, and upset (forced) pressurebecome the most largest factors. It should be noted that the data of No.18 shown in Table 2 are the results of pressure welding test on atitanium rod having the same size instead of the rod made by SUS304.Furthermore, Table 3 indicates the effects at the time when nickel wasintervened as a plating. TABLE 1 Major conditions of friction weldingParameter Setting conditions range Friction pressure (P₁) 20-100 MPaFriction time (t₁) 1-60 seconds Upset pressure (P₂) 50-300 MPa Upsetmaintaining time (t₂) 1-30 seconds Main spindle rotation speed (N)40-260 m/min

TABLE 2 Typical Conditions for friction welding and evaluation ofwelding strength and welding zone cross section Friction weldingconditions Results of evaluation P₁ t₁ P₂ t₂ N Tensile strength SectionSpecial No (MPa) (sec) (MPa) (sec) (m/min) (N/mm²) microscope item 1 205 50 10 80 78.5 2 40 5 50 10 80 117.7 3 60 5 50 10 80 201.0 4 80 5 50 1080 196.1 5 60 10 50 10 80 220.7 6 60 20 50 10 80 205.9 7 60 10 100 10 80364.8 8 60 10 200 10 80 374.6 9 60 10 300 10 80 379.5 10 60 10 200 10130 578.6 A 11 60 10 200 10 220 598.2 A 12 60 10 200 10 260 588.4 A 1360 10 200 30 130 559.0 A 14 60 10 200 10 40 117.7 15 60 10 50 10 220152.0 16 60 2 150 10 130 551.2 A 17 60 2 150 5 130 571.7 A 18 60 2 150 5130 589.2 A Titanium member 19 CCM-B (chromium/zirconium copper) (forcomparison) 372.7Note)any one of tensile strength indicated in Table 2 is the average value ofnumber of repetition n = 5.A: there is neither void, nor non-welded area, but stable mixed layer(Section microscopy observation)

TABLE 3 Nickel-interposition effect Welding conditions; Conditionsbefore welding of P₁ 60 MPa members t₁ 5 seconds On the side of NumberP₂ 150 MPa On the side of stainless steel of T₂ 5 seconds copper rodTests N 130 m/min Plating but Same with the 1 592 MPa uncovered leftcell 2 481 MPa 3 519 MPa 4 491 MPa 5 554 MPa Nickel plating Plating but1 593 MPa (5 μm) uncovered 2 568 MPa 3 588 MPa 4 591 MPa 5 590 MPaNickel plating Plating but 1 490 MPa (60 μm) uncovered 2 484 MPa 3 463MPa 4 478 MPa 5 482 MPa

Example 2 Examination Experiment of Heat Affection by Measuring Hardnessof Copper Plate

The welding test piece of No. 11 in Table 2 was cut off in the directionof axis, and the welding section is resin-encasulated according to theconventional method as shown in FIG. 6. Micro-Vickers hardness wasmeasured at the site of the starting point and the place towards outsideat 6 mm measured from the starting point by setting the welding sectionto the starting point, in the direction of stainless steel rod and inthe direction of copper member, and by setting the shaft center to thestarting point. The heat-affected zone of heat input at the time whenthe friction welding was carried out was extremely limited, and suchheat-affected zones centralized to the welding zone are around 2.5 mm,respectively. TABLE 4 Hardness in the vicinity of pressure welding zone(Unit; Hv) Welding zone to copper Welding zone to stainless member steelCenter of 6 mm from the Center of 6 mm from the axis center of axis axiscenter of axis 0.2 mm 102.5 100.8 165.6 162.4 1.0 mm 98.3 99.7 222.1223.7 1.5 mm 110.4 109.8 239.1 256.1 2.0 mm 132.2 122.5 261.3 270.8 2.5mm 137.6 121.9 272.1 298.1 3.0 mm 135.9 138.3 280.6 302.9

However, the friction welding tests of Example 1 are only a kind ofsingle pressure welding test of copper plate and stainless steel rod,respectively. In the case of the actual casting mold, there are a numberof stud bolts or mounting holes with respect to one surface of moldpiece. Then, we have decided that the simulation test in which its sizeis similar to the short side size for the actual slab is used wascarried out, and this state will be described below in Example 3.

Example 3 Preparation of False-casting Mold

CCM-B (used in the fixed side) made of Chuetsu Metal Works Co., Ltd.whose sizes are 280 mm width, 800 mm length, and 25 mm thickness wasprepared, and welded using laterally 3 rows and in the direction oflength 9 rows of the stud bolts (used in the movable side) made ofSUS304 whose sizes are 14 mm diameter and 65 mm length. The pressurewelding conditions were set to the followings: main spindle rotationspeed 130 m/min, contact pressure 60 MPa, friction time 5 seconds, upsetpressure 150 MPa after setting the main spindle rotation speed to 0m/min by working the brake, and upset time 5 seconds. After pressurewelding was carried out, the perpendicular degrees of the stud boltswere measured, and the measured values were all within 0.07 mm.Incidentally, these are extremely excellent mounting precision withrespect to the arc stud welding in which the variation of about 1.6 mmis generated in the case where the stud bolt having the same length isused. Moreover, thermal deformation of the copper plate was scarcelyobserved. At 10 places, the sampling was randomly performed from thecopper plate after the welding, and served as tensile test pieces. Then,the welding strengths were measured on such pieces to show strength of450 MPa or more in all of the cases. It should be noted that all of thefracture points corresponded to “copper+SUS304”, and an excellentinterface welding state was indicated.

Three pieces of the test pieces were separately selected from theremaining portions which were not subjected to the test, and voids andnon-welding portions were not observed at all in the observation of thewelding portion from the cross section. Therefore, it could be verifiedthat the friction welding could be fully employed in the manufacturingprocess of the casting mold.

INDUSTRIAL APPLICABILITY

For the conventional steel continuous casting mold, a copper plate whichis unnecessarily thick has been utilized since there is a constraintthat a back frame for water cooling is mounted. As a result of this, forthe purpose of improving thermal conductivity, it has been essential toconduct such extra auxiliary working for providing a cooling groove onthe side of the copper plate. On the other hand, according to thepresent invention, for example, an example of mold in which a mountinghole of a back frame is provided on the side of the casting mold, asshown in FIG. 5. If a boss made of stainless steel is subjected tofriction welding, at least tread cutting processing to the rear surfaceof the mold and subsequent helisert attachment become unnecessary.Moreover, as ripple effects, not only the copper plate as a whole can bethinned but also the cutting processing of the cooling groove itself canbe made unnecessary. It should be noted that in the case where it ismore effective for uniform solidification of molten steel that the flowof the cooling water is rate-determined, the stock back frame can beversatile without remaking it in a novel fashion by making a platehaving a cooling groove interposed between the mold rear surface and theback frame. Therefore, it leads to the significant reduction ofindustrial waste generated as a result of used copper material,furthermore, and also leads to the shortening of a large amount ofprocessing time. Thus, the total economic effects thereby cannot bemeasured.

On the other hand, in a so-called bolt attached casting mold in which astud bolt is welded by an arc stud welding method, it is possible that astud bolt with flux of which tip has been bevel processed can besubstituted with a usual stud bolt, and thus ferrule is not necessary,too. Therefore, the cost can be reduced, and there is no generation ofthe industrial waste, too. Furthermore, in addition to these, the heataffection to the mold copper plate is given only on the extreme surfacelayer, while void-free welding is achieved, and the heat deformation ofcasting mold after the welding, the lowering of the welding strength,and variation in the welding strength can be suppressed. Moreover, sinceinclination of a bolt (perpendicular degree) can be also prevented,there can be provided a casting mold and a method of manufacturing thesame which can be made null of post-leveling processing and boltbreakage incident and the like and are extremely useful in theindustries. Moreover, needless to say, the present invention can also beapplied even the case where small members of any type of stainless steelor titanium member are welded.

Particularly, if the friction welding method is applied under thelimited welding conditions, heat-affection which has an influence uponcopper or a copper alloy can be localized in the extreme interface ofthe welding section, at the time when bolts for back frame mounting madeof stainless steel or mounting seat are welded on the anti-molten steelcontact surface of the casting mold, that is, on the contact surface(rear surface) with the cooling water, in a steel continuous casting.Thus, while heat deterioration, heat deformation, and further weldingdefects of copper or a copper alloy is prevented, the ripple effectsmake it possible to save a large scale of resources by integrating it inan excellent precision with a strong strength without assembling ortrouble at the time when used.

1. A mold welded with a dissimilar metal member, characterized in thatthe mold is manufactured by a method comprising a first step ofpressingly bringing the dissimilar metal member into contact with a moldformed of copper or a copper alloy in a stationary state while rotatingthe dissimilar metal member at a high speed, a second step of stoppingthe dissimilar metal member, and a third step of providing a forcedpressure larger than the pressure in the first step to the mold.
 2. Themold according to claim 1, characterized in that the mold is a steelcontinuous casting mold.
 3. The mold according to claim 1, characterizedin that the dissimilar metal member is a back frame mounting member. 4.The mold according to claim 3, characterized in that the back framemounting member is equipped with a screw structure for interiorlymounting the back frame.
 5. The mold according to claim 2, characterizedin that the steel continuous casting mold is a steel continuous castingmold for electromagnetic stirring.
 6. The mold according to claim 1,characterized in that main rotation speed of the dissimilar metal memberof the first step is 60 m/min or more, the pressure is 40 MPa or more,and the forced pressure of the third step is 60 MPa or more.
 7. The moldaccording to claim 1, characterized in that the dissimilar metal membercomprises a stainless steel, titanium, a titanium alloy or a nickelalloy.
 8. The mold according to claim 1, characterized in that when amold and a dissimilar metal member are brought into contact with eachother, a nickel plating layer or a nickel alloy plating layer, or anickel foil or a nickel alloy foil is intervened between the moldsurface and the dissimilar metal member surface.
 9. The mold accordingto claim 8, characterized in that the thickness of a plating layer or afoil is in the range from 1 to 50 μm.
 10. A method of manufacturing amold welded with a dissimilar metal member characterized in that themethod comprises a first step of pressingly bringing the dissimilarmetal member into contact with a mold formed of copper or a copper alloyin a stationary state while rotating the dissimilar metal member at ahigh speed, a second step of stopping the dissimilar metal member, and athird step of providing a forced pressure larger than the pressure inthe first step to the mold.
 11. A method of manufacturing a mold weldedwith a dissimilar metal member, characterized in that while performingpressure welding of the mold and the dissimilar metal member, said moldand mold metal member are subjected to solid state welding by frictionheat generated by the difference of both main spindle rotation speeds.12. The method of manufacturing according to claim 11, characterized inthat the surface area of welding surface including welding site of amold which consists of copper or a copper alloy is 100-fold or more ofthe welded area of a dissimilar metal member.
 13. A steel continuouscasting mold in which a back frame mounting member is welded by frictionwelding.
 14. The mold according to claim 2, characterized in that thedissimilar metal member is a back frame mounting member.
 15. The moldaccording to claim 14, characterized in that the back frame mountingmember is equipped with a screw structure for interiorly mounting theback frame.